Virtual guard bands

ABSTRACT

A radio resource scheduler at a first base station may be configured to: identify radio frequency resources in use by the first base station, identify radio frequency resources to be reserved as virtual guard bands to reduce adjacent band interference, and install virtual guard band rules for reducing interference with adjacent bands. The virtual guard band information may be hints, allocations, priorities, reservations, or scheduling instructions for avoiding certain radio resources, radio resource blocks, or frequencies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit of anearlier filing date under 35 U.S.C. § 120 based on, U.S. patentapplication Ser. No. 15/149,941, filed May 9, 2016, and entitled“Virtual Guard Bands,” which itself claims the benefit of priority under35 U.S.C. § 119(e) of U.S. Provisional Patent Application No.62/158,192, filed on May 7, 2015 and entitled “Virtual Guard Bands,” andU.S. Provisional Patent Application No. 62/166,401, filed on May 26,2015 and entitled “Inter-Cell Interference Coordination,” which arehereby incorporated by reference in their entirety for all purposes. Thepresent application also hereby incorporates by reference U.S. patentapplication Ser. No. 14/542,544, “Adjacent Channel InterferenceCancellation in Multi-Channel Systems,” filed Nov. 14, 2014; U.S. patentapplication Ser. No. 14/642,544, “Federated X2 Gateway,” filed Mar. 9,2015; and U.S. patent application Ser. No. 14/828,432, “Inter-CellInterference Mitigation,” filed Aug. 17, 2015, each in its entirety forall purposes.

The following documents are also incorporated by reference in theirentirety for all purposes: 3GPP TS 36.331, version 10.7.0, “RadioResource Control (RRC); Protocol specification”; 3GPP TS 36.331, version8.21.0, “Radio Resource Control (RRC); Protocol specification”; 3GPP TS36.314, version 9.1.0, “Layer 2—Measurements”; 3GPP TS 36.214, version10.1.0, “Physical Layer; Measurements”; 3GPP TS 23.203, version 10.4.0,“Policy and charging control architecture”; 3GPP TS 37.803-b10, version11.1.0, “Mobility enhancements for Home Node B and Home enhanced NodeB”; 3GPP TS 36.423, version 10.1.0, “X2 Application Protocol (X2AP)”;3GPP TS 36.600, “E-UTRA and E-UTRAN; Overall Description”; and 3GPPRel-10_description_20140630.

BACKGROUND

In a situation wherein backhaul and access radio interfaces areco-located and/or in the same radio band, it is difficult to isolate theinterfaces to avoid or prevent cross-interference with each otherwithout bulky, expensive, and power-hungry filters and amplifiers.

Typically, a guard band is an intentionally unused part of the radiospectrum between two radio bands, or on either side of a singledesignated radio band, left unused for the purpose of preventinginterference. By separating two wider frequency ranges, guard bands helpto ensure that both can transmit simultaneously without interfering witheach other. Typically, in order to ensure that certain frequencies arenot used, filters are required.

LTE has built-in guard bands between designated bands. In LTE, guardbands of 1 MHz on either side of a designated band are common. As LTE issensitive to interference, rigorous filtering is required for theseguard bands, which requires high-performance and expensive filters.

Fractional frequency reuse (FFR) and/or inter-cell interferencecoordination (ICIC) are techniques used in wireless networks forreducing interference. In particular, interference is reduced for usersat the edge of a base station's coverage region (called cell edgeusers). As implied by the name of the technique, interference in a givencell is reduced by coordination of potentially interfering transmissionsfrom a base station in another cell.

SUMMARY

In one embodiment, a system is disclosed, comprising: a radio resourcescheduler at a first base station configured to: identify radiofrequency resources in use by the first base station, identify radiofrequency resources to be reserved as virtual guard bands to reduceadjacent band interference, and install virtual guard band rules forreducing interference with adjacent bands; and a base stationcoordination node in communication with the base station configured to:answer queries regarding radio frequencies in use by neighboring basestations; receive virtual guard band information from the first basestation; and send virtual guard band information to a second basestation.

The virtual guard band information may be hints, allocations,priorities, reservations, or scheduling instructions for avoidingcertain radio resources, radio resource blocks, or frequencies. Theradio resource scheduler may be coupled to an access transceiver and abackhaul transceiver, each at the first base station, and each having adifferent radio frequency transmission band. The radio resourcescheduler may be configured to identify radio frequency resources in useby nearby base stations or other nearby sources of interference. Thevirtual guard band information may be shared across multiple basestations. The virtual guard band information may be shared acrossmultiple base stations using communication between the multiple basestations using an X2 protocol. The virtual guard band information may beshared across multiple base stations using the base station coordinationnode. The base station coordination node acts as a gateway between thebase station and a core network. A radio resource scheduler at a secondbase station can also be configured to receive non-overlapping frequencyallocation information from the base station coordination node.

In another embodiment, a method is disclosed, comprising: for a basestation transmitting in an allocated frequency band that is adjacent toan adjacent in-use frequency band, consulting a device configuration todetermine what frequency bands are assigned for use by the base station;assessing a nearby radio frequency environment for interferingfrequencies; identifying a virtual guard band of radio resources withinthe allocated frequency band that cause less interference totransmissions in the adjacent in-use frequency band; and installingrules in a scheduler at the base station to reduce use of the identifiedvirtual guard band radio resources.

The method may further comprise reducing interference by allocatingfrequencies at a base station coordination node for each of a first anda second base station, such that the frequencies used by the first basestation do not overlap the frequencies used by the second base station.The method may further comprise dynamically adjusting the virtual guardbands. The method may further comprise identifying a radio resource thatshould not be used and communicating it via an X2 protocol message to asecond base station. The method may further comprise increasingutilization of resource blocks in a middle or far end of an allocatedfrequency band relative to a set of frequencies in the virtual guardband.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a virtual guard band, in accordancewith some embodiments.

FIG. 2 is a flowchart of an exemplary method, in accordance with someembodiments.

FIG. 3 is a schematic diagram of an enhanced base station, in accordancewith some embodiments.

FIG. 4 is a schematic diagram of a signaling coordinator server, inaccordance with some embodiments.

FIG. 5 is a system architecture diagram of an exemplary networkconfiguration, in accordance with some embodiments.

DETAILED DESCRIPTION

In some embodiments, inter-cell interference cancellation (ICIC)techniques may be used to create virtual guard bands. Virtual guardbands may provide a lower noise floor for arbitrary frequency bandsadjoining a frequency band designated for use. The virtual guard bandsmay provide the effect of radio frequency filtering without the use of ahardware filter. Alternately, virtual guard bands may be used inconjunction with a hardware filter to lower the required performancespecifications of the hardware filter.

The ICIC techniques may include the use of X2 communications betweenbase stations or cells, optionally through an intermediary coordinationnode. One ICIC technique that may be used is to send a request from asource to a target base station to register certain resource blocks(RBs) or subcarriers, as if the source base station would like to usethose resource blocks or subcarriers. This causes the resource blocks tobe designated for non-use at the target base station. The ICICtechniques may also include the use of time domain coordination, as wellas frequency domain coordination. 3GPP Release 10 Enhanced ICIC (eICIC)is specifically designed to permit time domain coordination inheterogeneous networks, and may be used in conjunction with the methodsdescribed herein in some embodiments. Interference may be mitigated oncontrol channels as well as traffic channels, with or without the use ofenhanced ICIC, in some embodiments.

Virtual guard bands may be used in certain embodiments where receive andtransmit antennas, multiple antennas, multiple transmitters, or evenmultiple base stations, etc., are co-located in the same physicallocation or even in the same device. In such cases, virtual guard bandsmay enable acceptable performance in such otherwise-challengingenvironments. Such a situation may occur for a femto cell combined witha wireless backhaul link. In some embodiments, a greater guard band maybe provided over what is required by the 3GPP specification.

In some embodiments, ICIC across different LTE bands, specifically, theleading and trailing edges of the mid band, may be used to lower thenoise floor on the band edge. X2 may be used as the protocol forcoordinating the ICIC functionality between two or more cells. ICIC maybe coordinated by a central server, for example, a coordinating nodesituated between the base stations and a core network, as describedherein.

In some embodiments, various ICIC methods may be used to lower the noisefloor on the band edge, thereby relaxing the required specification ofthe filters in the system. For example, in the case that an upper bandabove the access band is used for the backhaul link, X2-managed ICIC maybe used to lower the noise floor for the leading edge (˜2620 MHz) of theaccess link filter, by assigning for use fractional frequencies that areon the lower end of the mid band, so that downlink transmissions aresent via an isolated portion of the mid band. In the case a lower bandbelow the access band is used for backhaul, X2-managed ICIC may assignfractional frequencies at the upper end of the mid band. Other examplesof ICIC are also known and may be used.

The function of assigning resource blocks is typically performed by ascheduler at an eNodeB. In some embodiments, resource blocks may beassigned for use by a central scheduler located in the network at acoordinating node managing several eNodeBs, thereby enabling thecreation of virtual guard bands. The guard bands are virtual because thebands are physically allocated for use for the operator, but are notused based on rules present at the scheduler. The virtual guard bandsare dynamic in that they may be turned on and off and made larger andsmaller as needed. In some embodiments, a central coordinating node mayprovide hints, allocations, priorities, reservations, or otherinformation to enable a scheduler at the edge of the network in aneNodeB to perform scheduling while ensuring that the scheduling providesvirtual guard bands.

In some embodiments, a rule-based system may be used to identify whichresource blocks, subcarriers, or frequencies should be avoided. Theinput to the rule-based system can be a set of frequencies that is inuse. For example, a base station configured to use 2.4 GHz Wi-Fi forwireless backhaul may use the specific Wi-Fi channel to identify virtualguard bands, or frequencies that should be avoided for use. The virtualguard bands may then be incorporated into scheduling of resources atthat base station or at neighboring base stations.

Coordination of virtual guard bands may be possible within a single basestation, in some embodiments. For example, a base station may be amulti-radio access technology (multi-RAT) base station, and may use both2.4/5 GHz Wi-Fi and 3G/4G radio frequencies. One RAT may be used forbackhaul (providing connectivity to a core network or the Internet) andanother RAT may be used for access (allowing handsets and other userdevices to connect to the base station for connectivity). When using aparticular 3G/4G band, or Wi-Fi channel, the base station may identifywhether a virtual guard band is appropriate between the access radio andthe backhaul radio.

Coordination of virtual guard bands may also be possible across multiplebase stations, in some embodiments. For example, the base stationdescribed in the preceding paragraph may be part of a mesh network ofsimilar base stations. To prevent interference of the base stations withone another, the base stations may communicate their operating frequencybands and resource allocations to each other, and/or may communicatevirtual guard bands that should not be used to each other. Communicationmay occur directly via, e.g., point-to-point microwave links, or mayoccur via internet protocol (IP) routing through the mesh network.Communication may involve the use of an X2 protocol extension.

Coordination of virtual guard bands may also be possible across multiplebase stations using a coordinating node, in some embodiments. Forexample, the mesh network of base stations described in the precedingparagraph may be in communication with a centralized coordinationserver. The coordination server may perform one or more of the functionsdescribed herein, including: identifying the bands in use at one basestation or across multiple base stations; identifying appropriate guardbands based on the bands in use; and sharing the resource allocationsand/or the virtual guard bands/resource exclusions across multiple basestations. The coordination server may use an X2 protocol extension ormay use an S1 protocol extension.

In some embodiments, a highly linear transmitter on a complementarymetal-oxide semiconductor (CMOS) chip may be combined with an off-chipstandalone power amplifier. The off-chip PA is permitted to have arelaxed filter specification by the use of a highly linear Tx signalchain with digital pre-distortion (DPD) for the on-chip Tx, whichreduces adjacent channel leakage. The on-chip Tx is also configured tohave increased output power and efficiency within a specific range, suchas between 0 dBm to 10-15 dBm, and/or output power of up to 15+ dBm.This leaves 6-10 dB gain to be obtained in the off-chip PA, furtherpermitting the off-chip PA to have a relaxed filter specification. Thisenables the use of a lower-cost, smaller off-chip PA.

CMOS transmitters exist that provide this type of high linearity usingDPD, power of 15+ dBm, and nearly 50% peak efficiency, and are suitablefor pairing with many off-chip PAs. The greater efficiency of thetransmit chain reduces power draw by the transmit chain itself, but alsopermits the use of a more efficient off-chip PA. In some embodiments,filtering may be provided at a receive end; in some embodiments,filtering may be provided at a transmit end.

In some embodiments, three tunable filters (low band, mid band and upperband) can dynamically (at configuration time) cover the low, mid, andupper bands individually. These filters may be situated in the on-chiptransmit chain, in some embodiments, and in fact may be best suitedbefore the PA in the transmit chain. A separate duplexer may be used forband 41. Three of the same filter may also be used, wherein each istuned to a different center frequency.

As an example, for a desired 15 dB backhaul/access directional antennaseparation, and the 0.127 m minimal separation, 22 dB free space pathloss is permitted. We can derive the 80 dB stopband attenuation from thedynamic range requirements. In the Rx path, we can use an active high-Q(Q>400) bandpass filter, combined with a active Tx jammer cancellationcircuit, to achieve over 60 dB rejection at around 25 MHz offset withfairly low cost. More accurate calibration and tuning may achieve higherrejection at closer frequency separation, up to 80 dB and beyond.

The use of tunable filters may benefit in that the system describedherein may be used with a variety of spectral bands, or may be used withone set of bands in one location and another set of bands in anotherlocation.

In one embodiment, a coordinating node, such as a Parallel Wireless LTEAccess Controller (LAC), which may be located in a core network, iscoupled with each of a first and a second base station, which may be LTEbase stations (eNodeBs), and which may also be Parallel WirelessConverged Wireless Systems (CWSes) with additional wireless capability,such as Wi-Fi backhaul and/or access capability. The LAC may have an X2interface connection to each CWS.

The two CWSes may produce interference with each other for a userequipment (UE), by causing the UE to be fed by both CWS signals. Thiscell-edge UE has poor signal from both CWS 1 and CWS 2, which meansthere will be interference, high error rate, impacting user performance.With the help of variable attenuators, a reduced throughput effect canbe viewed at a test bench using monitoring equipment on the UE and/or atthe base station. The CWSes may also send information to the LACpertaining to, e.g., UE performance metrics such as throughput, and/orerror rate. The CWS can send the information, e.g., pertaining tointerference/throughput, from the CWS at the LAC, via the X2 interface.In some embodiments, a method using variable attenuators to simulateinterfering base stations may be used to test performance of ICIC asdescribed herein.

In some embodiments, the LAC may have a command line interface and maybe able to turn on ICIC functionality via a command line. When ICIC isenabled, the LAC may send ICIC information to either or both CWSes. TheICIC information may be a request to start ICIC, or informationpertaining to an ICIC process performed at the LAC, or schedulinginformation for performing ICIC, or some combination of the above, orother ICIC information. This ICIC information may be sent via the X2interface connection to each CWS.

In some embodiments, the LAC may run an algorithm and decide what isbest for each CWS, in some cases attempting to enable each CWS to get afair amount of throughput. The LAC may also send back informationguiding each CWS, so that each CWS can schedule at its node such thatthere will be less error rate and increased performance for the celledge user.

A network operator may use the disclosed systems and methods to improveperformance and user experience for users in challenged cell edgeconditions and enable dense heterogeneous networks. Improved handoverrate and better VoLTE quality may also be obtained. Use of adjacentfrequency bands and Wi-Fi channels may also be enabled.

System design can thus enable the use of relatively inexpensive filtersto achieve high performance.

In a further embodiment, fractional frequency reuse (FFR) may beenhanced using the techniques described herein. For example, the basestation may be using an FFR scheme in which cell edge users are assignedfrequencies that do not interfere with the cell edge users ofneighboring cells. A particular cell may utilize a frequency band thatis adjacent to another frequency band. Within the FFR-identifiedfrequency band, the base station may identify a virtual guard band suchthat a portion of the FFR-identified frequency band is avoided orexcluded from use in order to provide improved signal performance forthe adjacent cell. The portion of the FFR-identified frequency band thatis closest to the adjacent cell's frequency band would be avoided orexcluded from use. In some embodiments, this exclusion may be performedat a resource block level by requiring a scheduler to follow certainrules. The scheduling rules may be hard rules or soft rules, in that therules may be configured to be relaxed, for example, when the channel iscongested and additional capacity is needed.

In a further embodiment, a white space database, such as the Google TVWhite Space Spectrum Database, may be consulted by an automated processto identify which frequencies are in use in the physical vicinity of thetransmitting station. The white space database may be used to identifywhich frequencies or radio resources are available to the current basestation.

In some embodiments, an element management system could be used toprovision frequencies to be used as virtual guard bands. An elementmanagement system may be used to manage various characteristics of basestations in the network, and may also be used to identify specific bandsthat are used by each base station in the network.

In some embodiments, virtual guard bands may be identified at a radioresource planning phase.

In some embodiments, information may be shared that may includeidentification of a radio frequency resource that is in use followed byidentification of radio resources that should not be used.

In some embodiments, identification of a radio resource that should notbe used, and communicating it via a coordinating message, such as an X2protocol message, to one or more other base stations.

In some embodiments, a base station transmitting in a given frequencyband that is adjacent to another in-use frequency band can identifyradio resources within the given frequency band that cause the leastinterference to transmissions in the adjacent in-use frequency band.This may entail, for example, using resource blocks or frequencysubcarriers that are higher or lower in frequency than might beidentified in an ordinary resource reservation process. This may entailincreasing the number of resource blocks or frequency subcarriers thatare in use in the middle or far end of an allocated frequency band, insome embodiments.

FIG. 1 is a schematic diagram of a virtual guard band, in accordancewith some embodiments. Bands 101-106 as shown are frequency bands thatare allocated for service, shown roughly in proportion to their size andarranged in order from lower frequency to higher frequency. Band 101 isa lower band of U.S. regulatory band 41, which is a time-divisionduplexed band used in the United States for Federal CommunicationsCommission (FCC) broadband radio service (BRS) and educational broadbandservice (EBS). Band 102 is a mid band of FCC band 41 (BRS/EBS). Band 103is an upper band of the same band. Bands 104-106 are shown overlappingwith bands 101-103 because they are coextensive in frequency. Band 104is an uplink band for 3GPP Band 7, defined by 3GPP TS 36.101 for LTE andTS 25.101 for UMTS, and each incorporated herein in its entirety. 3GPPbands used in the LTE standard are designed to use different bands foruplink and downlink, and for those bands to be separated by a space(also sometimes called a guard band). Band 105 is not used by 3GPP Band7 but is instead used by 3GPP Band 38. Band 106 is the downlink band for3GPP band 7. Band 38 is a time-division duplexed (TDD) band. Band 7 is afrequency-division duplexed (FDD) band.

Below frequency bands 101-103 and 104-106, a filter configuration isshown. Filter 107 and filter 109 are used for an upper band for abackhaul link of a base station. Filter 107 is for downlink transmissionand filter 109 is for uplink transmission. Filter 110 and filter 112 areused for a lower band for a second backhaul link of the same basestation or a different base station. Filter 110 is for uplinktransmission and filter 112 is for downlink transmission. Filter 107 isused to provide radio frequency (RF) filtering for a frequency used byan access link. Filter 109 is used for RF filtering for a backhaul link.Filters 107 and 109 are on one RF transceive chain and filters 110 and112 are on another RF chain (thus filters 107 and 112 are applied to thesame frequencies but are independent). The two receive chains may be ona single base station, or on two base stations.

As depicted, the real-world performance of each of filters 107, 109,110, 112 is not perfect. Some energy that is not filtered out fromadjacent bands leaks into the receive chain; this is shown by thewidening base of the filter in the diagram. Overlapping section 108 is afrequency range where neither filter 107 nor filter 109 is able tocompletely block RF energy from the adjoining band. Frequencies in thisfrequency range experience interference, low signal-to-noise ratios, anddegraded performance. Similarly, overlapping section 111 is a frequencyrange where neither filter 110 nor filter 112 can completely block RFenergy from the adjoining band. Where the words “overlap” or“overlapping” are used herein, they may be understood to mean physicallyoverlapping, simultaneously in use, currently interfering, orpotentially interfering.

Overlapping sections 108 and 111 are thus good candidates for theapplication of a guard band. However, in some cases a literal guard bandis not possible to deploy between frequency blocks 104 and 105, orbetween frequency blocks 105 and 106. For example, a base station may beusing both FCC band 41 and 3GPP band 7, or using both 3GPP bands 7 and38. In this case a virtual guard band may still be used.

Using a virtual guard band entails reducing the use of overlappingfrequency ranges, such as frequency ranges 108 and 111. This reductionmay be accomplished by identifying what radio interference is in thearea, identifying a subset of a prior-selected frequency band thatshould not be used (the virtual guard band), and transmitting on asubset of frequencies that is not part of the virtual guard band,thereby refraining from transmission on those frequencies. Thisreduction may also be accomplished by using this virtual guard band at ascheduler in the base station. This reduction may also be accomplishedby communicating this virtual guard band across multiple base stationsusing, for example, an X2 coordination protocol. This reduction may alsobe accomplished by sharing this virtual guard band across multiple basestations using a coordinating node.

The size of overlapping frequency ranges 108 and 111 is determined bythe passband performance of RF filters 107, 109, 110, 112. Accordingly,the size of a required virtual guard band may be assessed in conjunctionwith RF sampling, to determine how much energy is being radiated alongwhat frequencies, and with RF passband profiling of filters embedded inthe base stations. In the absence of other information, a guideline of10% of frequencies above and below the desired frequency band may beused to establish parameters for a virtual guard band.

FIG. 2 is a flowchart depicting a method for using a virtual guard band,in accordance with some embodiments. At step 201, a device configurationis consulted to determine what frequency bands are assigned for use bythis device. For example, a base station may access its ownconfiguration files to determine that it has both a 2.4 GHz Wi-Fibackhaul radio and a 4G LTE Band 7 access radio. Step 201 may alsoinclude profiling of one or more RF filters in the device to determinewhether an operational effectiveness of one or more filters wouldbenefit from the use of a virtual guard band. At step 202, the nearby RFenvironment may be assessed. For example, one or more of the followingmay be assessed: the RF environment at the same device (202 a); thenetwork environment at nearby base stations (202 b); consulting acoordinating node for further information (202 c).

Step 202 a may include, for example, noting that a particular basestation uses both LTE and Wi-Fi, and that the LTE band in use isadjacent to a Wi-Fi channel, and providing the specific frequencies inuse to the next step 203. Step 202 a may also include, for example,noting that the base station is using two adjacent Wi-Fi channels foraccess and backhaul or for uplink and downlink. Step 202 a may alsoinclude, for example, noting that a powerful transmit RF chain isadjacent to a less-powerful receiver. Step 202 a may also involveactivating an RF sniffing capability using a hardware RF transceiverfunctionality, to determine what frequencies are in use at the presentdevice.

Step 202 b may include, for example, identifying interferingtransmission bands at nearby base stations. The list of nearby basestations may be determined from a user equipment (UE) measurementreport, neighbor relations table, or from a coordinating node. If acoordinating node is present, it may also be able to access informationregarding whether a virtual guard band is needed, or whether the signalstrength on a particular band at the nearby base station does notwarrant a virtual guard band (for example, if transmission strength at aneighboring base station is weak or if receive strength at the presentbase station is strong). In the case that a base station is in a meshnetwork, other nodes on the mesh network may be queried for RF usage.Information regarding load, congestion, data throughput, error rate,packet drop rate, radio signal strength including signal measurementssuch as signal-to-noise ratio and received signal strength indicators(RSSIs), may be obtained.

Step 202 c may include, for example, connecting to a coordinating nodeand getting information about the network. If the coordinating nodemanages the network, it may have complete information abouttransmissions and frequency bands in the area. If the coordinating nodedoes not manage the network or is managing only a subset of the network,the coordinating node may still have information from several other basestations about current and local network conditions.

At step 203, specific frequencies, resources, or resource blocks thatconstitute a virtual guard band may be identified, by determiningwhether each frequency block is in an overlapping frequency range asdescribed above. These resources may then be marked not to be used bythe scheduler in step 204. The scheduler may be a Wi-Fi scheduler or anLTE scheduler, or a combined scheduler, in some embodiments. Multipleschedulers may be in use for different transceivers, and in this casethe virtual guard band instruction may be sent to the appropriatescheduler. The instructions may be installed in the scheduler as apersistent rule to be used during every scheduling window, in someembodiments, so that the rule takes effect over more than onetransmission time interval (TTI). In some embodiments, these resourcesmay be marked not to be used except under certain circumstances. In someembodiments, these resources may be not be marked but may rather be sentto the back of the queue for allocation, so that they are allocatedafter other resources in the queue have been allocated. These rules maybe installed at the scheduler in the base station. The scheduling rulesmay operate in conjunction with fractional frequency reuse (FFR) rules.In some embodiments, the rules may be set to apply only to transmissionsfrom a particular device, such as the device running the method.

At step 205, the assessment of the nearby network environment may besent to the coordinating node, which may collect all of the reportednetwork environment reports, and may use these to change what bands itreports as in use. Similarly, the identified virtual guard bandresources may be sent to the coordinating node. Similarly, thescheduling rules may be sent to the coordinating node. The coordinatingnode itself may perform the same steps shown in FIG. 2, and may provideone or more of network environment information, virtual guard bandinformation, and scheduling rule information specific to one or morebase stations, so that at any time a base station may consult thecoordinating node and obtain one or more of these types of informationto be installed at the base station. This information may constitutehints, allocations, priorities, reservations, or another method forspecifying scheduling-related information. The coordinating node mayalso perform scheduling of radio resources on behalf of one or more basestations, in some embodiments, and may install rules according to thismethod to accommodate a virtual guard band in its scheduler.

Other sources may also be consulted at step 202 for relevantinformation. For example, a public radio white space database may beconsulted to determine whether frequencies are being used adjacent tothe ones identified as allocated for use at step 201. As anotherexample, the frequency bands of LTE, UMTS, and others are well-known andare specified in 3GPP technical standards, IEEE technical standards,etc. Virtual guard bands may be set up to reduce usage of radioresources at the edge of the bands allocated for use, even absent anyinterference. This may be useful to relax a filter specification of anRF filter in the device (or may compensate for a relaxed filterspecification in the device).

FIG. 3 is a schematic diagram of an enhanced base station, in accordancewith some embodiments. Enhanced base station 300 may be an eNodeB foruse with LTE, and may include processor 302, processor memory 304 incommunication with the processor, baseband processor 306, and basebandprocessor memory 308 in communication with the baseband processor.Enhanced eNodeB 300 may also include first radio transceiver 310 andsecond radio transceiver 312, internal universal serial bus (USB) port316, and subscriber information module card (SIM card) 318 coupled toUSB port 314. In some embodiments, the second radio transceiver 312itself may be coupled to USB port 316, and communications from thebaseband processor may be passed through USB port 316.

In some embodiments, processor 302 may be coupled to a globalpositioning system (GPS) module 330. GPS module 330 may provideinformation to the processor regarding the location of the mobile basestation. GPS module 330 may be connected to a GPS antenna 331 locatedoutside the device, preferably on the top or roof of the exterior of avehicle in which the base station is mounted, so that the GPS antennacan receive signals from GPS satellites. In some embodiments, the GPSmodule may provide AGPS functionality, and may cooperate with one ormore other wireless modules, such as a Wi-Fi module, to obtainadditional information. In environments where the use of the mobile basestation is anticipated on a moving vehicle that is underground or out ofsight of the sky, another positioning system may be used in conjunctionwith GPS/AGPS so that the position of the mobile base station may beascertained at times when GPS is not available. For example, a subwaytrain outfitted with a mobile base station may use other means, such asbeacons on the track, to determine position. The position calculated bythe GPS module 330 is processed by the processor 302, in someembodiments, to determine velocity. In some embodiments the GPS modulecan provide the velocity directly.

In some embodiments, processor 302 may be coupled to a CAN bus interface340, which in turn may be coupled electrically to a vehicle CAN bus 341of the vehicle in which the mobile base station is mounted. The CAN businterface may monitor the CAN bus for vehicle-wide notifications,particularly power-related notifications. The CAN bus interface may alsotrack and store battery information over time, and may also model theperformance of the battery over time, so as to enable processor 302 toknow if power down is imminent, even without an explicit notificationfrom the vehicle power controller.

Processor 302 and baseband processor 306 are in communication with oneanother. Processor 302 may perform routing functions, and may determineif/when a switch in network configuration is needed. Baseband processor306 may generate and receive radio signals for both radio transceivers310 and 312, based on instructions from processor 302. In someembodiments, processors 302 and 306 may be on the same physical logicboard. In other embodiments, they may be on separate logic boards.

The first radio transceiver 310 may be a radio transceiver capable ofproviding LTE eNodeB functionality, and may be capable of higher powerand multi-channel OFDMA. The second radio transceiver 312 may be a radiotransceiver capable of providing LTE UE functionality. Both transceivers310 and 312 are capable of receiving and transmitting on one or more LTEbands. In some embodiments, either or both of transceivers 310 and 312may be capable of providing both LTE eNodeB and LTE UE functionality.Transceiver 310 may be coupled to processor 302 via a PeripheralComponent Interconnect-Express (PCI-E) bus, and/or via a daughtercard.As transceiver 312 is for providing LTE UE functionality, in effectemulating a user equipment, it may be connected via the same ordifferent PCI-E bus, or by a USB bus, and may also be coupled to SIMcard 318.

SIM card 318 may provide information required for authenticating thesimulated UE to the evolved packet core (EPC). When no access to anoperator EPC is available, local EPC 320 may be used, or another localEPC on the network may be used. This information may be stored withinthe SIM card, and may include one or more of an international mobileequipment identity (IMEI), international mobile subscriber identity(IMSI), or other parameter needed to identify a UE. Special parametersmay also be stored in the SIM card or provided by the processor duringprocessing to identify to a target eNodeB that device 300 is not anordinary UE but instead is a special UE for providing backhaul to device300.

Wired backhaul or wireless backhaul may be used. Wired backhaul may bean Ethernet-based backhaul (including Gigabit Ethernet), or afiber-optic backhaul connection, or a cable-based backhaul connection,in some embodiments. Additionally, wireless backhaul may be provided inaddition to wireless transceivers 310 and 312, which may be Wi-Fi302.11a/b/g/n/ac/ad/ah, Bluetooth, ZigBee, microwave (includingline-of-sight microwave), or another wireless backhaul connection. Anyof the wired and wireless connections may be used for either access orbackhaul, according to identified network conditions and needs, and maybe under the control of processor 302 for reconfiguration.

Other elements and/or modules may also be included, such as a homeeNodeB, a local gateway (LGW), a self-organizing network (SON) module,or another module. Additional radio amplifiers, radio transceiversand/or wired network connections may also be included. The SON modulemay be configured to provide transmit power increase/decreasefunctionality, radio band switching functionality, or communicationswith another remote SON module providing, for example, these types offunctionality, in some embodiments. The SON module may be used toperform the steps of FIG. 2 and may execute on the general purposeprocessor 302.

Processor 302 may identify the appropriate network configuration, andmay perform routing of packets from one network interface to anotheraccordingly. Processor 302 may use memory 304, in particular to store arouting table to be used for routing packets. Baseband processor 306 mayperform operations to generate the radio frequency signals fortransmission or retransmission by both transceivers 310 and 312.Baseband processor 306 may also perform operations to decode signalsreceived by transceivers 310 and 312. Baseband processor 306 may usememory 308 to perform these tasks.

FIG. 4 is a schematic diagram of a signaling coordinator server, inaccordance with some embodiments. Signaling coordinator 400 includesprocessor 402 and memory 404, which are configured to provide thefunctions described herein. Also present are radio access networkcoordination/signaling (RAN Coordination and signaling) module 406, RANproxying module 408, and routing virtualization module 410. In someembodiments, coordinator server 400 may coordinate multiple RANs usingcoordination module 406. In some embodiments, coordination server mayalso provide proxying, routing virtualization and RAN virtualization,via modules 410 and 408. In some embodiments, a downstream networkinterface 412 is provided for interfacing with the RANs, which may be aradio interface (e.g., LTE), and an upstream network interface 414 isprovided for interfacing with the core network, which may be either aradio interface (e.g., LTE) or a wired interface (e.g., Ethernet).Signaling storm reduction functions may be performed in module 406.

Signaling coordinator 400 includes local evolved packet core (EPC)module 420, for authenticating users, storing and caching priorityprofile information, and performing other EPC-dependent functions whenno backhaul link is available. Local EPC 420 may include local HSS 422,local MME 424, local SGW 426, and local PGW 428, as well as othermodules. Local EPC 420 may incorporate these modules as softwaremodules, processes, or containers. Local EPC 420 may alternativelyincorporate these modules as a small number of monolithic softwareprocesses. Modules 406, 408, 410 and local EPC 420 may each run onprocessor 402 or on another processor, or may be located within anotherdevice.

FIG. 5 is a system architecture diagram of an exemplary networkconfiguration, in accordance with some embodiments. Base stations 502and 504 are connected via an S1-AP and an X2 interface to coordinationserver 506. Base stations 502 and 504 are eNodeBs, in some embodiments.Coordination server 506 is connected to the evolved packet core(EPC)/Core Network 508 via an S1 protocol connection and an S1-MMEprotocol connection. Coordination of base stations 502 and 504 may beperformed at the coordination server. In some embodiments, thecoordination server may be located within the EPC/Core Network 508.EPC/Core Network 508 provides various LTE core network functions, suchas authentication, data routing, charging, and other functions. In someembodiments, mobility management is performed both by coordinationserver 506 and within the EPC/Core Network 508. EPC/Core Network 508provides, typically through a PGW functionality, a connection to thepublic Internet 510.

In some embodiments, the radio transceivers described herein may be basestations compatible with a Long Term Evolution (LTE) radio transmissionprotocol or air interface. The LTE-compatible base stations may beeNodeBs. In addition to supporting the LTE protocol, the base stationsmay also support other air interfaces, such as UMTS/HSPA, CDMA/CDMA2000,GSM/EDGE, GPRS, EVDO, other 3G/2G, legacy TDD, or other air interfacesused for mobile telephony. In some embodiments, the base stationsdescribed herein may support Wi-Fi air interfaces, which may include oneor more of IEEE 802.11a/b/g/n/ac/af/p/h. In some embodiments, the basestations described herein may support IEEE 802.16 (WiMAX), to LTEtransmissions in unlicensed frequency bands (e.g., LTE-U, LicensedAccess or LA-LTE), to LTE transmissions using dynamic spectrum access(DSA), to radio transceivers for ZigBee, Bluetooth, or other radiofrequency protocols, or other air interfaces. In some embodiments, thebase stations described herein may use programmable frequency filters.In some embodiments, the Wi-Fi frequency bands described herein may bechannels determined by the respective IEEE 802.11 protocols, which areincorporated herein to the maximum extent permitted by law. In someembodiments, the base stations described herein may provide access toland mobile radio (LMR)-associated radio frequency bands. In someembodiments, the base stations described herein may also support morethan one of the above radio frequency protocols, and may also supporttransmit power adjustments for some or all of the radio frequencyprotocols supported. The embodiments disclosed herein can be used with avariety of protocols so long as there are contiguous frequencybands/channels. Although the method described assumes a single-in,single-output (SISO) system, the techniques described can also beextended to multiple-in, multiple-out (MIMO) systems.

Those skilled in the art will recognize that multiple hardware andsoftware configurations may be used depending upon the access protocol,backhaul protocol, duplexing scheme, or operating frequency band byadding or replacing daughtercards to the dynamic multi-RAT node.Presently, there are radio cards that can be used for the varying radioparameters. Accordingly, the multi-RAT nodes of the present inventionmay be designed to contain as many radio cards as desired given theradio parameters of heterogeneous mesh networks within which themulti-RAT node is likely to operate. Those of skill in the art willrecognize that, to the extent an off-the shelf radio card is notavailable to accomplish transmission/reception in a particular radioparameter, a radio card capable of performing, e.g., in white spacefrequencies, would not be difficult to design.

Those of skill in the art will also recognize that hardware may embodysoftware, software may be stored in hardware as firmware, and variousmodules and/or functions may be performed or provided either as hardwareor software depending on the specific needs of a particular embodiment.

Although the scenarios for interference mitigation are described inrelation to macro cells and micro cells, or for a pair of small cells orpair of macro cells, the same techniques may be used for reducinginterference between any two cells, in which a set of cells is requiredto perform the CoMP methods described herein. The applicability of theabove techniques to one-sided deployments makes them particularlysuitable for heterogeneous networks, including heterogeneous meshnetworks, in which all network nodes are not identically provisioned.

In any of the scenarios described herein, where processing may beperformed at the cell, the processing may also be performed incoordination with a cloud coordination server. The eNodeB may be incommunication with the cloud coordination server via an X2 protocolconnection, or another connection. The eNodeB may perform inter-cellcoordination via the cloud communication server, when other cells are incommunication with the cloud coordination server. The eNodeB maycommunicate with the cloud coordination server to determine whether theUE has the ability to support a handover to Wi-Fi, e.g., in aheterogeneous network.

Although the methods above are described as separate embodiments, one ofskill in the art would understand that it would be possible anddesirable to combine several of the above methods into a singleembodiment, or to combine disparate methods into a single embodiment.For example, all of the above methods may be combined. In the scenarioswhere multiple embodiments are described, the methods may be combined insequential order, in various orders as necessary.

Although certain of the above systems and methods for providinginterference mitigation are described in reference to the Long TermEvolution (LTE) standard, one of skill in the art would understand thatthese systems and methods may be adapted for use with other wirelessstandards or versions thereof.

In some embodiments, the software needed for implementing the methodsand procedures described herein may be implemented in a high levelprocedural or an object-oriented language such as C, C++, C#, Python,Java, or Perl. The software may also be implemented in assembly languageif desired. Packet processing implemented in a network device caninclude any processing determined by the context. For example, packetprocessing may involve high-level data link control (HDLC) framing,header compression, and/or encryption. In some embodiments, softwarethat, when executed, causes a device to perform the methods describedherein may be stored on a computer-readable medium such as read-onlymemory (ROM), programmable-read-only memory (PROM), electricallyerasable programmable-read-only memory (EEPROM), flash memory, or amagnetic disk that is readable by a general or specialpurpose-processing unit to perform the processes described in thisdocument. The processors can include any microprocessor (single ormultiple core), system on chip (SoC), microcontroller, digital signalprocessor (DSP), graphics processing unit (GPU), or any other integratedcircuit capable of processing instructions such as an x86microprocessor.

Although the present disclosure has been described and illustrated inthe foregoing example embodiments, it is understood that the presentdisclosure has been made only by way of example, and that numerouschanges in the details of implementation of the disclosure may be madewithout departing from the spirit and scope of the disclosure, which islimited only by the claims which follow. Various components in thedevices described herein may be added, removed, or substituted withthose having the same or similar functionality. Various steps asdescribed in the figures and specification may be added or removed fromthe processes described herein, and the steps described may be performedin an alternative order, consistent with the spirit of the invention.Features of one embodiment may be used in another embodiment. Otherembodiments are within the following claims. For example, thecoordinating node may process incoming requests for virtual guard bandsusing a client-server request-based procedure, and may handle incomingrequests out of order based on the originating source base station ofthe request.

The invention claimed is:
 1. A system, comprising: a first base stationof a plurality of base stations; a second base station of the pluralityof base stations; and a radio resource scheduler at a coordinating nodeconfigured to: identify radio frequency bands in use by the first basestation, identify a radio access technology in use at the first basestation, determine that a desired band is adjacent to the identifiedradio frequency bands in use, identify virtual guard bands based on theradio access technology and the determination made that the desired bandis adjacent to the identified radio frequency bands in use, and sharethe virtual guard bands with the second base station, wherein the firstbase station and the second base station are each in communication witha core network over a first radio access technology (RAT) and are alsoeach allowing a user equipment (UE) to have connectivity with the corenetwork over a second RAT, thereby providing a lower noise floor foradjacent in-use frequency bands for the plurality of base stations. 2.The system of claim 1, wherein the virtual guard bands are allocations,priorities, reservations, or scheduling instructions for avoidingcertain radio resources, radio resource blocks, or frequencies.
 3. Thesystem of claim 1, wherein the radio resource scheduler is configured toidentify radio frequency resources in use by nearby base stations orother nearby sources of interference.
 4. The system of claim 1, whereinthe virtual guard bands are shared across multiple base stations.
 5. Thesystem of claim 1, wherein the virtual guard bands are shared acrossmultiple base stations using communication between the multiple basestations.
 6. The system of claim 1, wherein the radio resource scheduleris configured to dynamically turn virtual guard bands on or off, ordynamically increasing or decreasing the size of the virtual guardbands.
 7. The system of claim 1, wherein the first RAT is a Wi-Fi RATand the second RAT is either a Code Division Multiple Access (CDMA),Universal Mobile Telecommunications System (UMTS), or Long TermEvolution (LTE) RAT.
 8. A method for providing a lower noise floor foradjacent in-use frequency bands at a base station, comprising:identifying, at a coordinating node, radio frequency bands in use by acurrently-operating base station; identifying, at the coordinating node,a radio access technology in use at the currently-operating basestation; determining, at the coordinating node, if the radio frequencybands in use are adjacent to each other; assessing, at the coordinatingnode, a nearby radio frequency environment for interfering frequencies;identifying, at the coordinating node, based on the determined radioaccess technology and the determination made that the radio frequencybands in use are adjacent to each other, a virtual guard band of radioresources within the allocated frequency band that cause lessinterference to transmissions in the in-use radio frequency band;identifying, at the coordinating node, a radio resource that should notbe used and communicating the radio resource that should not be used viaan X2 protocol message to a second base station; and installing, at thebase station, rules in a scheduler to reduce use of the identifiedvirtual guard band radio resources.
 9. The method of claim 8, furthercomprising assigning, at the coordinating node, frequencies for use byat least two base stations of a plurality of base stations in adjacentcells, such that the frequencies used by the at least two base stationsof the plurality of base stations do not overlap.
 10. The method ofclaim 8, further comprising dynamically turning the virtual guard bandson or off, or dynamically making the virtual guard bands larger orsmaller in size.
 11. The method of claim 8, further comprisingincreasing utilization of resource blocks in a middle or far end of anallocated frequency band relative to a set of frequencies in the virtualguard band.
 12. The method of claim 8, wherein the base station is incommunication with a core network over a first radio access technology(RAT) and providing connectivity for a user equipment (UE) to the corenetwork over a second RAT.
 13. The method of claim 12, wherein the firstRAT is a Wi-Fi RAT and the second RAT is either a Code Division MultipleAccess (CDMA), Universal Mobile Telecommunications System (UMTS), orLong Term Evolution (LTE) RAT.
 14. The method of claim 8, furthercomprising sharing, at a base coordination node, the virtual guard bandinformation across multiple base stations using an X2 protocol.
 15. Themethod of claim 8, further comprising using, at the coordinating node,an inter-cell interference cancellation (ICIC) or enhanced ICIC (eICIC)time domain coordination technique at the first base station.
 16. Themethod of claim 8, further comprising lowering a noise floor on leadingand trailing edges of a mid band of an in-use frequency band at the basestation.
 17. The method of claim 8, further comprising lowering a noisefloor for leading edge of an access link filter by assigning fractionalfrequencies for use on a lower end of a mid band, thereby sendingdownlink transmissions via an isolated portion of the mid band.
 18. Themethod of claim 8, further comprising scheduling, at the coordinationnode, resource blocks for use at at least two base stations of aplurality of base stations.
 19. The method of claim 8, wherein thescheduler is a Wi-Fi scheduler, a Long Term Evolution (LTE) scheduler,or a combined Wi-Fi and LTE scheduler.